Overview

Consult the release notes

Before doing anything, stop and consult the release notes supplied with the new
version of the software. These detail bug fixes, new features and functionality,
and any particular points that may need to be noted during the upgrade process.

Backup first

It is imperative that, prior to attempting an upgrade of the database schema,
you take a complete backup of your wiki database and files and verify it. While
the upgrade scripts are somewhat robust, there is no guarantee that things will
not fail, leaving the database in an inconsistent state.

Perform the file upgrade

You can also obtain the new files directly from our Git source code repository.

Replace the existing MediaWiki files with the new. You should preserve the
LocalSettings.php file and the "extensions" and "images" directories.

Depending upon your configuration, you may also need to preserve additional
directories, including a custom upload directory ($wgUploadDirectory),
deleted file archives, and any custom skins.

Perform the database upgrade

As of 1.21, it is possible to separate schema changes (i.e. adding, dropping, or
changing tables, fields, or indices) from all other database changes (e.g.
populating fields). If you need this capability, see "From the command line"
below.

From the Web

If you browse to the Web-based installation script (usually at
./mw-config/index.php) from your wiki installation you can follow the script and
upgrade your database in place.

From the command line

From the command line, browse to the "maintenance" directory and run the
update.php script to check and update the schema. This will insert missing
tables, update existing tables, and move data around as needed. In most cases,
this is successful and nothing further needs to be done.

If you need to separate out the schema changes so they can be run by someone
with more privileges, then you can use the --schema option to produce a text
file with the necessary commands. You can use --schema, --noschema,
$wgAllowSchemaUpdates as well as proper database permissions to enforce this
separation.

Check configuration settings

The names of configuration variables, and their default values and purposes, can
change between release branches, e.g. $wgDisableUploads in 1.4 is replaced with
$wgEnableUploads in later versions. When upgrading, consult the release notes to
check for configuration changes which would alter the expected behavior of
MediaWiki.

Check installed extensions

Extensions usually need to be upgraded at the same time as the MediaWiki core.

In MediaWiki 1.14 some extensions were migrated into the core. Please see the
HISTORY section "Migrated extensions" and disable these extensions in your
LocalSettings.php

Test

It makes sense to test your wiki immediately following any kind of maintenance
procedure, and especially after upgrading; check that page views and edits work
normally, that special pages continue to function, etc., and correct any errors
and quirks which reveal themselves.

You should also test any extensions, and upgrade these if necessary.

Upgrading from 1.16 or earlier

If you have a Chinese or Japanese wiki ($wgLanguageCode is set to one of "zh",
"ja", or "yue") and you are using MySQL fulltext search, you will probably want
to update the search index.

In the "maintenance" directory, run the updateDoubleWidthSearch.php script. This
will update the searchindex table for those pages that contain double-byte Latin
characters.

Upgrading from 1.10 or earlier

If upgrading from before 1.11, and you are using a wiki as a commons repository,
make sure that it is updated as well. Otherwise, errors may arise due to
database schema changes.

Upgrading from 1.8 or earlier

MediaWiki 1.9 and later no longer keep default localized message text in the
database; 'MediaWiki:'-namespace pages that do not exist in the database are
simply transparently filled-in on demand.

The upgrade process will delete any 'MediaWiki:' pages which are left in the
default state (last edited by 'MediaWiki default'). This may take a few moments,
similar to the old initial setup.

Note that the large number of deletions may cause older edits to expire from the
list on Special:Recentchanges, although the deletions themselves will be hidden
by default. (Click "show bot edits" to list them.)

See RELEASE-NOTES for more details about new and changed options.

Upgrading from 1.7 or earlier

$wgDefaultUserOptions now contains all the defaults, not only overrides. If you
are setting this as a complete array(), you may need to change it to set only
specific items as recommended in DefaultSettings.php.

Upgrading from 1.6 or earlier

If upgrading from before 1.7, you may want to run refreshLinks.php to ensure
new database fields are filled with data.

Upgrading from 1.5 or earlier

Major changes have been made to the schema from 1.4.x. The updater has not been
fully tested for all conditions, and might well break.

On a large site, the schema update might take a long time. It might explode, or
leave your database half-done or otherwise badly hurting.

Among other changes, note that Latin-1 encoding (ISO-8859-1) is no longer
supported. Latin-1 wikis will need to be upgraded to UTF-8; an experimental
command-line upgrade helper script, 'upgrade1_5.php', can do this -- run it
prior to 'update.php' or the Web upgrader.

NOTE that upgrade1_5.php does not work properly with recent versions of
MediaWiki. If upgrading a 1.4.x wiki, you should upgrade to 1.5 first.
upgrade1_5.php has been removed from MediaWiki 1.21.

If you absolutely cannot make the UTF-8 upgrade work, you can try doing it by
hand: dump your old database, convert the dump file using iconv as described
here: http://portal.suse.com/sdb/en/2004/05/jbartsh_utf-8.html
and then re-import it. You can also convert filenames using convmv, but note
that the old directory hashes will no longer be valid, so you will also have to
move them to new destinations.

Message changes:

A number of additional UI messages have been changed from HTML to wikitext, and will need to be manually fixed if customized.

Upgrading from 1.4.2 or earlier

1.4.3 has added new fields to the sitestats table. These fields are optional and
help to speed Special:Statistics on large sites. If you choose not to run the
database upgrades, everything will continue to work in 1.4.3.

You can apply the update by running maintenance/update.php, or manually run the
SQL commands from this file:

maintenance/archives/patch-ss_total_articles.sql

Upgrading from 1.4rc1 or earlier betas

The logging table has been altered from 1.4beta4 to 1.4beta5 and again in 1.4.0
final. Copy in the new files and use the Web installer to upgrade, or the
command-line maintenance/update.php.

If you cannot use the automated installers/updaters, you may update the table by
manually running the SQL commands in these files:

As well as new messages, the processing of some messages has changed. If you
have customized them, please compare the new format using Special:Allmessages or
the relevant LanguageXX.php files:

copyrightwarning

dberrortext

editingcomment (was named commentedit)

editingsection (was named sectionedit)

numauthors

numedits

numtalkauthors

numtalkedits

numwatchers

protectedarticle

searchresulttext

showhideminor

unprotectedarticle

Note that the 1.3 beta releases included a potential vulnerability if PHP is
configured with register_globals on and the includes directory is served to the
Web. For general safety, turn register_globals *off* if you don't _really_ need
it for another package.

If your hosting provider turns it on and you can't turn it off yourself, send
them a kind note explaining that it can expose their servers and their customers
to attacks.

Upgrading from 1.2 or earlier

If you've been using the MediaWiki: namespace for custom page templates, note
that things are a little different. The Template: namespace has been added which
is more powerful -- templates can include parameters for instance.

If you were using custom MediaWiki: entries for text inclusions, they will *not*
automatically be moved to Template: entries at upgrade time. Be sure to go
through and check that everything is working properly; you can move them
manually or you can try using moveCustomMessages.php in maintenance/archives to
do it automatically, but this might break things.

Also, be sure to pick the correct character encoding -- some languages were only
available in Latin-1 on 1.2.x and are now available for Unicode as well. If you
want to upgrade an existing wiki from Latin-1 to Unicode you'll have to dump the
database to SQL, run it through iconv or another conversion tool, and restore
it. Sorry.

Upgrading from 1.1 or earlier

This is less thoroughly tested, but should work.

You need to specify the *admin* database username and password to the installer
in order for it to successfully upgrade the database structure. You may wish to
manually change the GRANTs later.

If you have a very old database (earlier than organized MediaWiki releases in
late August 2003) you may need to manually run some of the update SQL scripts in
maintenance/archives before the installer is able to pick up with remaining
updates.